Control system for railway air-compressors.



C. l. AXTELL.

CONTROL SYSTEM FOR RAILWAY AIR COMPRESSORS.

APPLICATION FILED FEB. 41 l9l6.

Patented Jan.30,1917.

, Inventor: Clinton J.. T

UNITED STATES PATENT OFFICE.

CLINTON J. A XTELL, F SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMIANY, A CORPORATION OF NEW YORK.

CONTROL SYSTEM FOR RAILWAY AIR-COMPEESSORS.

Specification of Letters latent.

Patented Jan. 30, 1917.

Application filed'lebruary 4, 1916. Serial No. 76,134.

J. AXTELL,

new and useful Improvements in Control Systems for Railway Air-Compressors, of whichvthe following is a specification.

My invention relates to the control of electrically driven railway air compremors such as are commonly utilized on electric railway cars and locomotives.

The driving motors of such air compressors are commonly connected to a supply of power by means of an electro-magnetic switch or contactor, whose coil is energized from some convenient source of power by means of some independent switch, which is commonly pressure-actuated and responsive. to the pressure conditions of the air system. Where such equipments are applied to railway cars or locomotives which are intended to be operated in multiple, a synchronizing wire is usually employed to interconnect the control circuits of the contactors on each car between said contactor coils and the pressure-actuated governor switches. It then follows that a closure of the contacts of any one of the governor switches will be suflicient to set in operation the compressors of all of the cars. This synchronizing wire is usually included in a cable running between the cars along with other control wires, and for this reason it is very essential that the potential upon the synchronizing wire shall be so small that no serious trouble will result in case this wire becomes accidentally crossed with any of the other control wires. In order to secure a supply of current of low voltage for these compressor control contactors, a dynamotor or a resistance upon .each car may be used. With such an arrangement,'however, it has been found that if the trolley upon one of the cars is lowered, then the dynamotor or the resistance and the Winding of the compressor control contactor on this car would constitute a ground connection for the synchronizing wire, so that the compressors upon the other cars would be operated continuously, without regard to the position of the governor contacts. In order to avoid this difiiculty of a back circuit, which would hold in the compressor contactors regardless of the position of the governor contacts, I provide a protective relav, responsive to the voltage supplied to the compressor contactor, which controls the connection of the winding of this contactor to the synchronizing wire.

My invention will be better understood from the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a diagram illustrating the ap-' plication of my invention to a train of two cars, A and B, theequipments of the two cars being identical; Fig. 2 is a modification.

As shown in Fig. 1 of the drawing, the air brake cylinders 1 are connected to the train pipe 2 which is supplied with compressed air from the reservoirs 3 through the reservoir equalizing pipe 4 and the motormans valves 5 in the usual manner, the reservoirs 3 being connected to and supplied with compressed air from the compressors 6.

Each air compressor 6 is driven by an electric motor 7, one terminal of Whichis connected to the return circuit by being grounded at 8, while the other is connected by a conductor 9, the contacts of the compressor contactor 10, conductor 11, and 'a switch 12 to a suitable source of current. Current for the compressor contactor is in this instance supplied from the trolley 13 through a series resistance 14, and the potential strain upon the same is further reduced by the provision of a low potential ground connection 17 connected to that side of the actuating Winding of the contactor 10 which is connected to the source of supply. This ground connection is made through a resistance 18, which should be of such proportions that the voltage drop across the same is very small in comparison with the trolley voltage, and is preferably less than the voltage supplied to the train wires for the other control apparatus At the same time, the relative resistances of the resistance member 18 and the winding of the contactor 10 are such that when the contactor winding is connected with a return circuit, for example, by being grounded through the contacts 20, 21 of the pressure responsive governor 19, sufiicient current will be diverted through this winding to cause the contactor to close. A synchronizing wire 16 is employed, as formerly, which runs throughout the length of the train and, therefore, connects the cars A and n. 'ihe other side of the windings of the compressor contactors 10 are adapted to be connected to the synchronizing wire 16 by means of the contacts of the protective relay 15, whosecwinding may be connected in series with the winding of the compressor contactor 10, and if so connected it will be seen that the same resistance 14: may be utilized for both.

If desired, the dynamotor 24, as illustrated in Fig. 2, may be employed as a potential reducing means in place of the resistances 14: and 18, and it so employed, it will be seen that the lower half thereof, which I have designated by the numeral 27, constitutes a low potential connection to ground which corresponds to that formed by the resistance 18 and ground connection 17. With such an arrangement, it will generally be found preferable to arrange the protective relay in the manner shown in Fig. 2, so that its actuating winding is practically in parallel with that of the contactor 10, instead of connecting it in series, as in the arrangement shown in Fig 1. With this arrangement the danger of a backcircuit will be equally well avoided.

In Fig. 1, the contacts 20 of the governors 19 are shown as connected to the winding of the compressor contactor 10 at a point intermediate the same and the contacts of the protective relay 15. In Fig. 2, however,

I have shown how this connection may be equally well made directly to the synchroniz ing wire without in any wa atfecting the operatlon and utility of my invention.

If, now, the pressure in any one of the reservoirs 3 is sufliciently reduced, then the spring of the corresponding governor will force its contacts together so that the com:

pressor contactor on that particular car will be energized. If voltage is applied from the trolley to the control circuits of theother car, then the protective relay on that car will be closed and the'compressor contactor associated therewith will likewise be energized. This operation will be carried out regardless of whetheror not the operation of the governors on the various cars is simultaneous. If, however, the voltage supplied to the control circuits of any car, as, for ex ample, car B, in which the switch 12 has been shown open, fails suddenly, then it will be seen that there is no possibility-that a back circuit can be formed which will hold in the compressor contactors on that car, for the reason that any current flowing from the synchronizing wire 16 must pass through the contacts of the protective relay 15 before it reaches the coil of the contactor 10.

I have illustrated and described my invention in what I now consider the best embodiment thereof, but it will be apparent to those skilled in this art that the arrangement and connections of the various parts are susceptible of much variation, and I, therefore, aim in the appended claims to cover all modifications which are within the scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In combination, a source of supply one side of which is grounded, a plurality of electric motors, electromagnetic switches having one side of their actuating windings connected to the ungrounded side of said source, and arranged to connect each of such motors to the source of supply, independent switches associated with each motor connected to the other side of said actuating windings for controlling the energization of the corresponding electromagnetic switches, a-low potential ground connection connected to the first mentioned side of each of said actuating windings, a synchronizing wire connected to the other side of each of said actuating windings, and means responsive to the voltage supplied to said electromagnetic switches controlling the connection of the actuating windings thereof to said synchronizing wire,

2. In combination, a source of supply one side of which is grounded, a plurality of electric motors, electromagnetic switches having one sideof their actuating windings connected to the. ungrounded side of said source, and arranged to connect each of such motors to the source of supply, independent switches associated with each motor connected to the other side of said actuating windings for controlling the energization of the corresponding electromagnetic switches, a low potential ground connection connected to the first mentioned side of each of said actuating windings, a synchronizing wire connected to the other side of each of said actuating windings, and protective relays responsive to the voltage supplied to said electromagnetic switches having their actuating windings connected in series with the windings of said switches, and having their contacts controlling the connection of the windings of said electromagnetic switches to said synchronizing wire.

- 3. In combination, a compressed air sys-.

tem, a plurality of motor-driven air com-' pressors supplying compressed air thereto,

a. source of electric current one side of which 1 tuating windings, a synchronizing wire connected to the other side of each of said actuating windings, and means responsive to the voltage supplied to said electromagnetic switches controlling the connection of the windings thereof to said synchronizing wire.

4. In combination, a plurality of cars, a compressed air system thereon supplied by motor driven compressors on two or more of said cars, a trolley wire, electromagnetic contacto rs arranged to connect each of said motors to the trolley wire, pressure actuated switches associated with each compressor arranged on a decrease of pressure in said system to complete an energizing circuit for the corresponding contactor, a train wire interconnecting the circuits of said contactors at points intermediate the actuating windings thereof and said pressure actuated switches, the other terminals of said windings being connected to the trolley wire through a resistance and the coil of a protective relay, the contacts of said protective relay controlling the connection of the windings of said contactors to said train wire, and resistance connections to ground intermediate the coils of said contactors and said relays.

In witness whereof, I have hereunto set myhand this 3rd day of February, 1916. e

CLINTUN J. AXTELL. 

